The present invention relates generally to an improved heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, thermal storage system, air cooler or air heater. More specifically, the present invention relates to a combination or combinations of separate indirect and direct evaporative heat exchange sections
or components arranged to achieve improved capacity and performance.
The invention includes the use of a plate type heat exchanger as an indirect heat exchange section. When compared with coil circuit indirect heat exchangers which are comprised of individual circuits of tubing, the performance of an indirect heat exchange section comprised of a plate type heat exchanger is improved. Such indirect heat exchange section can be combined with a direct heat exchange section, which usually is comprised of a fill section over which an evaporative liquid such as water is transferred, usually in a downwardly streaming operation. Such combined indirect heat exchange section and direct heat exchange section together provide improved performance as an overall heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater.
Part of the improved performance of the indirect heat exchange section comprising a plate heat exchanger is the capability of the indirect heat exchange section as a plate type heat exchanger to provide both sensible and latent heat exchange with the evaporative liquid which is streamed or otherwise transported over and through the indirect heat exchange section. Another important improvement is that plate heat exchangers will have more surface area in the same physical space as other evaporative indirect heat exchangers. Such as indirect heat exchangers comprised, of serpentine coils.
Various combinations of the heat exchange arrangements are possible in accordance with the present invention. Such arrangements could include an arrangement wherein the indirect heat exchange section operates alone, is physically located above the direct heat exchange section or is physically located below the direct heat exchange section. In such an arrangement with indirect section located above the direct section, an evaporative liquid is streamed or otherwise sprayed downwardly onto the indirect heat exchange section with such evaporative liquid, which is usually water, then exiting the indirect section to be transported over the direct heat exchange section which is usually comprised of a fill arrangement. In another arrangement of a combined heat exchange apparatus the indirect heat exchange section is physically located below the direct heat exchange section. In another arrangement of a combined heat exchange apparatus two or more indirect sections are placed in a single closed circuit fluid cooler or heat exchanger each above or below a direct heat exchange section is also part of the present invention. Further, it should be understood that due to varying heat loads and needs of heat exchange, the heat exchanger apparatus or fluid cooler of the present invention could be operated wherein both air and an evaporative liquid such as water are drawn or supplied across both the indirect and direct heat exchange sections. It may be desirable to operate the heat exchanger without a supply of the evaporative liquid, wherein air only would be drawn across the indirect heat exchange section. It is also possible to operate a combined heat exchanger in accordance with the present invention wherein only evaporative liquid would be supplied across or downwardly through the indirect heat exchange section and the direct heat exchange section, and wherein air would not be drawn by typical means such as a fan.
In the operation of an indirect heat exchange section, a fluid stream passing through the internal openings in the plate type heat exchanger is cooled, heated, condensed, or evaporated in either or both a sensible heat exchange operation and a latent heat exchange operation by passing an evaporative liquid such as water together with air in passages between individual plate pairs or cassettes in the indirect heat exchanger. Such combined heat exchange results in a more efficient operation of the indirect heat exchange section. The evaporative liquid, which again is usually water, which passes across or downwardly through the indirect heat exchange section then passes, usually downwardly, across or through the direct heat exchange section which is typically a fill assembly. Heat in the evaporative liquid is passed to air which is drawn generally downwardly, upwardly or across the direct heat exchange section and outwardly from the closed circuit fluid cooler or heat exchanger assembly by an air moving system such as a fan. The evaporative liquid draining from the indirect or direct heat exchange section is typically collected in a sump and then pumped upwardly for redistribution across the indirect or direct evaporative heat exchange section. Of course, as explained above, the indirect and direct heat exchange sections can be reversed wherein, in the reversed situation where a direct heat exchange section would be located above an indirect heat exchange section, the evaporative fluid exiting the indirect section would be collected in a sump and pumped upwardly for distribution across the direct heat exchange section. Alternatively, only the indirect heat exchange section may be present.
Accordingly, it is an object of the present invention to provide an improved heat exchange apparatus, which could be a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, which includes an indirect heat exchange section and possibly a direct heat exchange section.
It is another object of the present invention to provide an improved heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, including an indirect heat exchange section that comprises a plate type heat exchanger.
It is another object of the invention to provide an improved heat exchange apparatus comprising a plate type heat exchanger with more surface area per volume than other evaporative indirect heat exchangers.